1. Field of the Invention
The subject matter disclosed generally relates to the field of laser diodes.
2. Background Information
Laser diodes are used in a variety of system applications. For example, laser diodes are used as a light source in fiber optic communication systems. It is generally desirable to increase the output power and energy efficiency of a laser diode.
FIG. 1 shows an exemplary construction of a laser diode 1. The laser diode 1 includes a layer of n-doped material 2 and a layer of p-doped material 3 that are separated by an active layer 4. The n-doped and p-doped layers create a diode junction. A current is injected into the laser diode 1 through a contact 5. The current induces a migration of electrons and holes from the n-doped 2 and p-doped 3 layers into the active layer 4. The holes and electrons recombine to create a stimulated emission of photons. The laser diode 1 may also have upper 6 and lower 7 cladding layers that create a waveguide for the light generated in the active layer 4.
Unfortunately, the p-doped layers of most laser diodes have a high optical absorption coefficient. The high absorption rate of light in the p-doped layers reduces the energy efficiency of the laser diode. The lower efficiency increases the current requirements. Higher current increases the heat generated within the laser diode and reduces the life of the device. P-doped layers also have higher electrical resistivity than n-doped layers, which further reduces the electrical-to-optical conversion efficiency.